Pick the right one — they are different models
2× uses a model trained on photographs. It keeps skin, fabric and foliage looking like themselves and does not over-sharpen noise into artefacts.
4× uses one trained on illustration: clean lines, flat colour, crisp edges. Run it on a photograph and faces go waxy; run the photo model on line art and the lines stay soft. The choice matters more than the number.
What it cannot do
It cannot recover something that was never captured. Text too small to read comes back as convincing letter-shaped marks that are not the original letters. A face at twelve pixels comes back as a face — just not that person’s.
Everything above the smallest details is genuinely improved. Everything at or below them is invention that looks right, which is worth knowing before you use the result as evidence of anything.
Why this one uploads and the resizer does not
Changing an image’s size is arithmetic and happens in your browser — that is the image resizer, and it sends nothing. Inventing detail that was never captured takes a trained model on a graphics card, which is why this one cannot.
Your file goes browser-to-storage on an address signed for five minutes, is read once by the machine doing the work, and is deleted along with the result after about three hours.
Frequently asked questions
How big can the result be?
A 5 MB input at 4× is a very large image and takes a while. If you only need a moderate increase, 2× is faster and usually looks better on a photograph.
Is this the same as the browser-based resizer on this site?
No. The image resizer changes the size arithmetically, in your browser, with nothing uploaded — it is the right tool for making something smaller or hitting an exact pixel size. This one invents detail, and needs a graphics card to do it.
Does it cost anything?
No, and there is no paid tier holding back the good model — the one that runs is the one described above. There is a limit on how many enlargements come from one network in an hour, which is there to keep the graphics card available rather than to sell you anything.
What happens to the picture afterwards?
It is read once by the machine doing the work and deleted, along with the enlarged copy, within about three hours. It is not kept, not looked at and not attached to an account, because there are no accounts.
Something wrong with this tool, or an idea for it? Tell us